Recent dramatic innovation in lithography technology for patterning in semiconductor production gives patterns with extremely fine line widths. For lithography, exposure was initially performed using i line and g line, resulting in broad line widths. This caused produced semiconductors to have low capacities. Recent technological development, however, has enabled the use of KrF excimer laser to give patterns with dramatically fine line widths. Thereafter, the development has been advanced with aiming at the application of ArF excimer laser having a still shorter wavelength, and exposure using ArF excimer laser has gone into actual use very recently. The exposure using KrF excimer laser employed conventional resins, i.e., novolac or styrenic resins. ArF excimer laser light, however, has a still shorter wavelength of 193 nm and, as having this wavelength, is absorbed by resins containing an aromatic moiety, such as the novolac and styrenic resins. To prevent this, resins for use in exposure to ArF excimer laser light have been replaced with those structurally containing no aromatic moiety, namely, replaced with alicyclic resins. Acrylic resins are mainly used as the alicyclic resins. The acrylic resins employ a mechanism in which acrylic acid is protected with a protecting group, the protected acrylic acid releases the protecting group by an acid generated upon exposure to be converted into and act as a carboxylic acid moiety, and this makes the resulting resin soluble in an alkali (alkali-soluble). Many of currently used protecting groups are alicyclic groups devoid of polar groups. The resins using these protecting groups by themselves have poor adhesion to a substrate and lack affinity typically for alkaline developers. As possible solutions to this, there is proposed a multiplicity of acrylic monomers including, as an ester moiety, a polar-group-containing alicyclic skeleton. Among them, acrylic monomers including an alicyclic skeleton containing a lactone ring as the polar group are evaluated to have high functionality and are used in great numbers. Part of such acrylic monomers can be found in Japanese Unexamined Patent Application Publication (JP-A) No. 2000-026446 (Patent Literature (PTL) 1). Monomers including an ester group of a monocyclic lactone ring are also proposed typically in Japanese Unexamined Patent Application Publication (JP-A) No. H10-274852 (PTL 2). These monomers including such a monocyclic ester group, however, lack etch resistance and seem to be not so frequently used, because the etch resistance is a function most required for resists. A technique called “immersion exposure” is currently under study. In the immersion exposure, space between a substrate and a pattern exposure system is filled with a high-density liquid. According to this technique, resist patterns are designed to be finer and finer, and with this, resist films tend to have smaller thicknesses. This induces strong demands for monomers having satisfactory etch resistance. In addition, resins containing a large amount of an alicyclic acrylic ester moiety containing a lactone ring suffer from poor solubility in organic solvents such as resist solvents. This also induces strong demands for resist-use resins having better solubility.
PCT International Publication Number WO2009/107327 (PTL 3) proposes the use of a polymer as a photoresist resin, where the polymer is prepared by polymerizing a vinyl monomer containing a ring including a cyano group and a lactone skeleton in molecule. Advantageously, this polymer is highly soluble in resist solvents and has excellent hydrolyzability. The polymer, however, is considered to be not always sufficient in affinity for alkaline developers.